Study On Shear Behavior Of Underground Arch Structures

With the rapid development of economy,increasing of construction,and less available urban land,the above-ground space has become more limited and more difficult to meet people's living needs.Underground space engineering has hence gained more attention.The arch structure as a good compression-type structure,has been widely used in underground engineering.The research on underground arches has been focused on the ultimate bearing capacity with little on the shear bearing.According to the published research,the effect of shear deformation on an arch structure can be up to 20%.So,it is very important to study the shear bearing capacity of arch structures.Based on the theory of material strength,the commonly used equivalent beam-column method,combined with the elastic buckling theory,this study proposes a method to calculate the shear capacity of reinforced concrete arches.ABAQUS program was used to analyze the arch considering the influences of thickness of backfill,density of backfill material,reinforcement ratio,arch span ratio,and cohesion of backfill material on arch's the shear capacity.Lastly,some rules related to the above influencing factors are proposed,based on the numerical simulation results,as follows.(1)On the basis of material strength theory and considering the combined action between the main arch ring and the physical composition above,the ultimate bearing capacity of arch structure is calculated by using the equivalent beam-column method.Furthermore,a formula for determining the shear bearing capacity of a reinforced concrete arch is derived.(2)A finite element model utilizing ABAQUS program is established to model the underground arch under different loading conditions.Under gravity loads,the stress analysisof arch structure is carried out by hand calculations and compared with the finite element results.(3)Considering the combined effects between the arch and the physical composition above and the five affecting factors mentioned above,the arch is analyzed,variation rules on shear bearing capacity are proposed,and combined effect coefficients reflecting the five influencing factors are obtained.(4)For each parameter,the shear stresses of arch structure are analyzed-and their influence on the shear capacity of arch structure is investigated.The results show that the shear stress decreases with increasing arch span/depth ratio,backfill thickness,soil,reinforcement ratio,and backfill cohesion,suggesting increasing shear capacity.However,this trend is reversed for backfill.With the increase of the backfill density,the shear bearing capacity of arch structure is gradually reduced.Based on this study,the effect of the backfill thickness has the greatest effect on the shear capacity of an arch structure,and its combined effect is also most obvious.